Aircraft heating system



V r p 194 5. H. .1. DE N. MCCOLLUM 4,

AIRCRAFT HEATING SYSTEM F iled March 7, .1942 2 Sheets-Sheet 1 MgJZe/V/ka ZZam 7 'April 24, 1945. J. DE McCOLLUM 2,374,606

' AIRCRAFT HEATING SYSTEM I Filjed March 7, 1942 2 Shets-Sheet 2 HZTQTEZ and air supplied toan description, reference-being 'panying drawings, in which:

Pig. 1 is a partly sectional ditic View "leadinc Patented Apia: 2 1, a 1945 4 funnel) STATES P. ikl'iilw'r .O'FRiCE l f r 2,374,606

srs'ram Henry the N. McGollum, Chicago, 111.; Thelma McCoilum executrlx of said Henry J. De N.

' McCollum, deceased ers of'the internal combustiontype.

. I In aircraft heating systems .using heaters of r 7 14 Claims. My invention relates generally to meme heating apparatus, and more particularly to combustible'hlixture control means'for aircraft heatthe internal. combustion type, the combustible mixture for the heater is frequently drawn from the engine fuel. mixture supply system, usually from the high pressure side of .the supercharger which draws the mixture from the carburetor and forces it to the engine cylinders. This m'hr- -tui'e is frequently too rich for satisfactory complete combustion in the heater. It is the prim ry Object o! my invention to provide means for controlling the richness of the mixture supplied to the heater in a heatingsystem of this character. i

. AIfurther object is to provide improved means for removing excess :{uel fr ;m a mixture of iueh int'rnal combustion t v heater. v

Aiurther object is to provide a simple and eiiective means for accurately reguiatingthe iuei .mlxture supplied to a heater, and thereby improve the eflecttveness of its operation under a wide variety 01 operating conditions. V 7 Other objects will appear from the following had-to the accomoi the heating system;

iinez -z Dim. liand' I Fig. 3 is a schematic view of a modified form oi the invention. Y

typeshown in copendins application, Serial No. 378,262, died February 10, 1941-, and as indicatedlby the heate'r'casin g in, orgnisy be o! the multipieunit type shown in my copending e pin I cation, Serial No. 377,182,-filed February 3, 1941;.

As shown, the heater casing in tormsa part 01' an air supply conduit having a ram portion",

a condenser and shutter chamberfll, 9. connectin; section It, and a delivery section It, leading to the pilotscompartment and to any other,

portion: of the aircraft requiring'a supply. of

heated air.

' Fig. 2 is a vertical sectional view talren, onthe iii; p video witnaconibustible s n d' ei c m ,pipe :2

- Application March 7, 1942, Serial No. 433,128

into the pipe is beyond theinne rwali thereof,

as shown in detail in my cop n ins pplication.

. Serial No. 410,031; filed September a, 194 .a short length of flexible hose "connects theilt ting with a conduit 34, which leads to the upper header 18o! a condenser 38.

The flow oi the mixture through the conduit 3 y controlled by avalve 39 which may be manually or electromagnetically operated. The condenser 38 comprises a plurality of tubes 40 connecting its upper header 36 with its lower header l2.

- The lower header 42 islconnected by a conduit.

44 with a separator II, the conduit 44 entering the upper cylindrical shell portion ll tangentially. The lower'portion o! the separator is formed by a'conical tunnel portion iii. A conduit 52 connects'the bottom 01 the portion with the reduced pressure side oi the supercharger 28. top of the separator l6, and the space within this skirt is in free communication with the intake pipe. 20.

Within the intake pipe 20 is located a bulb 86, which is connected by conduit 58 with an expansibie metal bellows One end of the bellows 80 is secured ,to a suitable fixed. bracket 62,

p y 35 The heater, which may, be oi the"singleunit while the movable end 01 the bellows is connected to one arm of a suitable pivoted bell crank N by. a rod. The other arm-o! the bell crank 64' is connected to a plurality-of pivotaliy mounted shutters 88 byan actuating link N.

The bulb B6 a suitable volatile liquid, such as ether, alcohol,- etc., Or a mixture thereof,

. which, upon being I raised to a predetermined temperature, generates suilicient vapor pressure to open the shutters ca, opening them to in l-eelsbulb i6 and bellows ii are intended as illustrameans for operating the shutters 68.

" of the operationoithe' thermostatic controls, itl wiliusuallybedesirabletohave thethermostatic controls desiznedtomaintain the-mixturein' The heating system will generally be operated only when the atmospheric temperature is relatively low. On the other hand, the fuel and air mixture suplied to the upper header :6 will gen-:

erally be considerably warmer than the atmos- Dhere, due to the agitation and compression effected-in the supercharger It.

Depending. upon the design oi heater ll, upon the gradeor fuel used, and upon the character the intake pipe 2| at a temperature in, the order A cylindrical'skirt depends irom the k ing extents as the temperature of the mixture. flowing through intake pipe. 20- increases. The

V tive of any suitable-temperature responsive motor.

of r. a saturated m st this temperature burns completely and emciently in thev heater II The heater leis provided with the usual electrical ignition and control means. Assuming that the controls have been operated to start theheater, by opening valve 3! and energizing the heater'ignition means, the usually supersaturated mixture of gasoline and air at a temperature above 20F. flows through the condenser 2! which is cooled by the cool atmospheric air entering the ram l2. The rate at which thecooling air flows through the condenser 38 is regulated by the thermostatically controlled shutters 68 soas to cool the fuel mixture to a temperature in the order of 20' F. with the result that some of the fuel vapor will condense through the conduit 52 and is returned to the low pressure side of the supercharger 28. The conduit 52 is of such diameter that it will easily carry all of the condensed fuel lmder all conditions of operation, but will not withdraw an appreciable portion of the fuel vapor and air mixture from the separator 46. Thus, a float-controlled valve at the liquid outlet of the separator 48 will ordinarily not be necessary.

The mixture of fuel vapor and air, with a minimum of entrained liquid particles, will flow through the conduit 20 to the combustion chamber of the heater l0 where it is ignited and burns in the usual manner to heat the air supplied to it through the connecting section ii, the heated air being discharged through the delivery section It to the .cabin and other parts of the aircraft to be supplied with heated air. The

products of combustion are discharged through the conduit 22, the partial vacuum existing at the outlet of this conduit assisting in such flow.

The air supplied to the heater is preheated to some extent by passing the tubes 40 of the condenser 38. The system is illustrated as havthermostatically controlled shutters are mutually conducive to satisfactory operation of the system because as .the atmospheric temperature denser isrequired and at the samdtimethe air flow through the heater should be reduced to permit the heater, with its rehtively constant heat delivery capacity, to heat the air discharged from the heater to the required temperature.

In and under certain opit may be defi ab to pa throughthechamberltoflifip "tionofthe'airtobeheamanditiswithinthe oontemplatim of myinventionto thus construct theapparahsfliatapoi'tionoftheairtobe heated by-pamesthe ml and'the con-'- trolshuttersl 'Theformoftheinruifionshownin 3, includes many of the elements shown in Fig. 1, and the same reference characters have been applied to corresponding parts. The modification. of Fig. 3 is simpler. than the system 80, and has its 'open end substantially at the throat thereof. The jet tube 82 has a.plurality of minute orifices formed therein at spaced intervals. The conduit 52 leading from the bottom 'of the separator 46 has an orifice plug 86- secured therein. The orifice in this plug may be of predetermined size or may be in the form of a needle'valve controlled orifice. I

The orifice 88 is of such size that fuel will tend to collect inthe bottom of the separator 46. The cooling air flowing past the condenser 38, not being controlled byv shutters, will, under most conditionsof operations at high altitudes, when the atmospheric temperature is very low, condense a relatively large proportion of the liquid fuel from the mixture. Since the orifice in the plug 85 will be chosen of such diameter that all of the condensed fuel will not "be drawn through the return conduit 52 .to the. supercharger, the accumulated liquid fuelin the separator 46 will rise to alevel generally de-' pendent upon the) atmospheric temperature.

That is, when the'atmospheric temperature is low, the level of the accumulated liquid fuel in the separator 46 will be high, and vice versa..

When the level ofthe liquid fuel in the eparator 46 is high, a substantial quantity will be drawn through the orifices 84 in the fuel jet tube 82, and thus again mixed with the air and fuel vapor mixture drawn through the Venturi nozzle 82-, under these circumstances enriching the mixture suflicientlyto insure efilcient combustion within the heater l0. Conversely, when the atmospheric temperature is high, and the liquid level in the separator 48 relatively low, a large numberof the orifices 84 will he uncovered so that the air and vapor mixture may be drawn there.- through and into the fuel jet tube 82 with a lesser quantity of liquid fuel. The amount of liquid fuel added to the mixture passing through the Venturi nozzle 80, will thus increase as the temperature decreases, and thereby automatically compensate for the reduced amount of fuel vapor mixed with the air entering-the Venturi nozzle 7 drops, a lower rate of air flow through the con- "at low temperatures. The fuel mixture is thus maintained 'sufilciently uniform for satisfactory combustion, irrespective of the atmospheric temperature, and this, result is accomplished without the'necessity of providing any thermostatic may be of graduated size and spacing, o a a obtain the desired proportion of fuel in the nture supplied to the heater atdifferent atmospheric temperatures. Instead of a fixed orifice in the plug than adjustable orifice may be pro- 'erating' aircraft at high altitudes.

vided to accomplish similar results. v

The apparatus of Fig. 3 hasthe'particular advantage that it does not have any moving which may fail to operate'properly at all times under the severe conditions encountered in opthe liquid .11- The meth a: pplying a combustible mixture of fuel and air to a heater of the internalcombustion type from the aircraft engine carbureting means which constitutes a source of excessively rich mixture which comprises, reducing the temperature of the rich mixture sufliciently to cause condensation of some of the fuel from the mixture, separating the liquid fuel from the remainder of the mixture, supplying said remainingmixture to the heater for combustion therea in, and adding liquid fuel to the mixture supplied to the heater at a rate increasing with an increase in the 'rate at which the fuel is condensed.

stantial condensation of the fuel, a liquid trap connected to said exchange device to receive the mixture and condensed liquid fuel therefrom, means for withdrawing the liquid fuel from said trap atra relatively constant rate, whereby the liquid level within said trap will be in. part determined by the rate of condensation of liquid aavaeoe fuel in said near me device, a conduit leading to said from said trap at a point above the liquid level therein for conveying a vaporized fuel and air mixture to the heater and means responsive to the level of the liquid fuel in said trap to supply liquid fuel to the mixture in said conduit at a rate increasing as the level of the liquid fuel in said trap is raised.

13. In an aircraft heating system for use in an aircraft having an internal combustion engine and a supercharger for supplying a combustible mixture to the engine, the combination of a heat exchange device, means for supp in a cooling medium to said device, a. liquid trap,- conduits leading from the high pressure side of said supercharger through said heat exchange device and 14. The combination set forth in claim 13 in l which the means for adding the liquid fuel to the mixture conveyed to the heater operates to sup- Ply the liquid fuel at an increased rate as the liquid fuel level in said trap increases.

HENRY J. DE N. MCCOILUM. 

